In the closure art may be found numerous examples of dispensing type closures where the outer closure shell is made with either a horizontal slide that align holes or a rotatable member that brings openings into alignment upon relative rotation. These are sometimes termed "sifter fitment" type closures when one of the openings is of restricted screen size and serves to "sift" the contents of the containers that are being dispensed. Others take the form of a movable "trap" chamber which may be set to receive or trap a single article such as a tablet, or measured quantity in the case of powdered coffee, from the interior of the container when in one position and upon movement to a second position will dispense this quantity or tablet while closing the top of the container against further acceptance of product from the container.
These dispensing closures, if applied over containers that are sealed with a membrane or metallic foil that is adhered to the container finish, would normally require removal of the closure and rupture of the membrane with reapplication of the closure to take advantage of the dispensing feature.
Obviously, when the closure is on the container, the consumer is not readily apprised of whether the foil or membrane is intact, indicating that the container has not been tampered with after sealing.
The sealing of an aluminum foil to the top of the finish, of a glass container has been the subject of several patents such as U.S. Pat. No 3,928,109, issued Dec. 23, 1975 and U.S. Pat. No. 4,396,655, issued Aug. 2, 1983. In these examples, the foil disc is formed with a heat activated material, such as an epoxy on one side, and the glass container is provided with a silane coupling agent over the rim or top of the finish which will react with the epoxy and make a vapor tight seal with the aluminum. These foils have been applied to the finish without any other supporting materials, but in some cases the foil has been supported by an annular plastic snap-on ring that locates the foil on the container after filling and holds it in place during the well-known induction type heating to activate the adhesive. The induction heating of foil disc is clearly shown in U.S. Pat. No. 3,928.109.
It would be possible to determine the integrity of this foil seal, if the container were marketed without any further cover, but due to the rather fragile nature of the foil, it is normally necessary to have a cover or cap over the foil, such as a snap cap or regular threaded cap, or perhaps a lug style closure that is frequently used with baby food jars. These overcaps must be removed in order to see the condition of the foil seal.
Tamper-indicating closure systems have become desirable and one which would work with a dispensing closure should be equally desirable.